Table of Contents
Understanding Wind Loads
Wind load is the force exerted by wind on structures. It creates positive pressure on windward surfaces, suction on leeward surfaces, and complex patterns around corners. Proper wind load analysis is critical for preventing structural failures during storms and hurricanes. The ASCE 7 standard provides design methods.
Wind pressure increases with the square of speed, making high winds exponentially more destructive. A Category 5 hurricane creates roughly 4 times the pressure of a Category 1, which is why damage increases so dramatically with wind speed.
Wind Pressure Formula
Where Kz is exposure factor, V is wind speed (mph), Cd is drag coefficient, A is area (ft²). The 0.00256 factor accounts for standard air density.
Basic Design Wind Speeds (ASCE 7)
| Region | Speed (mph) | Pressure @C (psf) |
|---|---|---|
| Interior US | 115 | 33.9 |
| Hurricane coast | 150 | 57.6 |
| South Florida | 170 | 74.0 |
| Guam | 195 | 97.4 |
Frequently Asked Questions
What is exposure category?
B = urban/suburban with obstructions. C = open terrain (most common). D = flat coastal. Higher exposure means higher wind loads due to less ground friction.
Why square of wind speed?
Kinetic energy = ½ρv². Doubling speed quadruples pressure. This makes hurricanes exponentially more destructive than moderate storms.
What drag coefficient for a building?
Flat plates: 1.2-2.0. Square buildings: 1.3-1.5. Round structures: 0.5-0.7. Signs: 1.2-1.5. Building codes provide specific values for each shape.